Windshield Wiper Arm with Hemmed Distal End

ABSTRACT

A wiper arm ( 100 ) for a wiper assembly of an automotive vehicle, the wiper arm ( 100 ) being formed in a single piece from a metallic blank ( 100 ′) and having an inner end portion ( 100   a ) of generally U-shaped configuration in cross-section that is formed by drawing the blank ( 100 ′) in a progressive die, and an outer end portion ( 100   b ) that is formed with a C-shaped configuration in cross-section, by hemming. The outer end portion ( 100   b ) has a central portion ( 130 ) with edge portions ( 132 ) that are reversely folded to underlie the central portion ( 130 ), edges of the edge portions ( 132 ) being disposed in close proximity to one another. An end portion ( 100   c ) of the outer end portion ( 100   b ) of the wiper ( 100 ) is reversely folded to be spaced from and underlie a portion of the outer end portion ( 100   b ) thereabove, and the end portion ( 100   c ) is provided with an opening ( 126 ) by which a wiper blade may be attached to, or removed from, the wiper arm ( 100 ).

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.11/248,818 filed on Oct. 12, 2005.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO SEQUENCE LISTING

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a wiper arm for an automotive windshield wipersystem. More particularly, this invention relates to a wiper arm of theaforesaid character of unitary construction with a narrow, thickenedfree or distal end of a double thickness that is formed by hemming.

2. Description of the Prior Art

Typical prior art windshield wiper arm assemblies 10 used on motorvehicles as shown in FIGS. 1 through 5 normally consist of a mountinghead 12, retainer arm 14 and wiper or arm rod 16, as well as, a tensionor a coil spring 20. The mounting head 12 is typically manufactured ofzinc or aluminum die cast. Typically the retainer arm 14 is formed fromsheet metal and stamped in a general U-shaped configuration as shown inFIGS. 4 and 5. The windshield wiper arm assembly 10 also has a wiperblade (not shown), which has a support bracket system and wiper stripretainer (not shown). The wiper blade is pivotally connected to thewindshield wiper arm assembly 10 through use of a hook like end 17 ofthe wiper rod 16 which engages between two lateral cheeks of the supportbracket system of the wiper blade (not shown). The fit with the supportbracket requires a sizing operation on the width of the hook like end 17so that it will properly fit between the two lateral cheeks of thesupport bracket it engages. The connection thus formed guides the wiperblade with the wiper strip over the glass windshield of the motorvehicle. The jointed connection and the support bracket system make itpossible for the wiper strip to adapt to a curvature of the windshield.A required contact pressure of the wiper strip on the vehicle windshieldis attained with at least the tension coil of the spring 20 which bracesthe mounting head 12 and the retainer arm 14 in conjunction with thewiper rod 16 through a toggle joint 21.

The shape of the individual components of the retainer arm 14 isinfluenced by various demands and stresses. Specifically, they should beas torsionally rigid, deflection-resistant, and as narrow in the fieldof view as possible, so that the wiper blade can be guided withoutvibration and under control over the vehicle windshield yet presentlittle hindrance to the field of view. The mounting head 12 transmitsthe drive moment from the drive axis A-A to the wiper blade, via theretainer arm 14 and the arm rod 16. It also forms part of the togglejoint 21, by way of which the mounting head 12 is braced with theretainer arm 14 by the tension spring 20 and pressed in the direction ofthe vehicle window. The greatest forces or moments arise in the mountinghead 12, both parallel to the window and perpendicular to the window.Further, deformations in the lower region of the retainer arm 14 have anespecially strong effect over the entire length and can cause unevenwiping speeds as a result of a spring effect. The mounting head 12 andthe first portion of the retainer arm 14 must therefore be embodied asespecially deflection-resistant and torsion-resistant.

In a wiping motion, the outward portion of the retainer arm 14 movespartly, and the wiper or arm rod 16 moves completely, through the fieldof view of the driver and as a result they must be made not only torsionand deflection resistant, but also especially narrow so that they impedeas little of the driver's view as possible. Further, the retainer arm 14should be shaped in such a way that it is not lifted away from thevehicle window by the air flow across the windshield.

To accommodate these various requirements, prior art windshield wiperarm assemblies 10 have a wide mounting head that may be made of zinc oraluminum die cast or sheet metal as well as a retainer arm 14 that isalso made of sheet metal which is relatively wide in the region of themounting head 12 that is, at the lower edge 22 of the field of view ofthe driver. Often, this portion of the retainer arm 14 is made with aninverted U-profile that is open towards the window as shown in FIG. 5.Such profile has a relatively strong resistance moment, and isespecially torsion and deflection resistant in this area while alsobeing able to accommodate the tension spring 20 which is concealed inthe U-profile. In the outward direction towards the free arm end of theretainer arm 14 where the retainer arm 14 connects with the wiper rod16, the retainer arm 14 tapers so that it is narrower in the field ofview of the driver as shown in the cross-section of FIG. 3. Over thefull length of the retainer arm 14, the profile has a constant materialthickness, determined by the sheet metal thickness used. This thicknessis designed in order to accomplish the appropriate dimensional stabilityunder the greatest material stresses to be expected which are basicallybending and torsion stresses, specifically, perpendicular and parallelto the vehicle window.

Generally, the wiper rod 16 is formed of a profile of constant thicknessmaterial solid flat stock, which is either crimped or riveted 30 asshown in FIGS. 1 and 3 to the retainer arm 14. The thickness of thewiper rod 16 is a function of drive and contact forces, the length ofthe retainer arm 14, as well as the resistant moments to the windshieldwiper arm assembly 10. Further considerations are the effect of windengagement faces as well and more importantly, the slender structure inthe field of view of the driver. Generally, the material stress demandsare greatest at the connection point of the wiper rod 16 to the retainerarm 14 and because of the small cross-sectional area and unfavorableresistance moments, the material thickness is generally determined bythe stress requirement at the connection point between the retainer arm14 and the wiper rod 16. For this reason, the wiper rod 16 itself isgenerally a solid stock formed of a thicker material than the retainerarm 14 thus, the arm rod 16 and retainer arm 14 are combined in a singlerigid assembly which rotates a limited degree about drive axis A-A. As aresult, in some applications, there is unnecessarily high consumption ofmaterial, high material costs, and high weight.

Further considerations to be made in the design of a complete windshieldwiper system is the associated windshield washing system andconsiderations which need to be made with respect to the mounting of thespraying device on the hood or the windshield wiper arm assembly 10. Thewindshield washing system consists of a washing liquid reservoir, aswell as a pump (not shown), by which washing liquid is sprayed onto thewindshield to be cleaned by a spraying device. It is known that thespraying device may be stationarily arranged on the engine compartmenthood. Further, the windshield cleaning system-spraying device may befixed to the windshield wiper arm assembly 10. The advantage of fixingthe spraying device to the windshield wiper arm assembly 10 is that thewashing liquid is sprayed immediately in front of the wiper blade. Inthe prior art embodiment illustrated in FIGS. 1 through 5, the mountingbracket 26 for attaching a spraying or washer nozzle 28 is riveted toone of the legs of the U-shaped retainer arm 14. In some prior artembodiments the mounting bracket 26 may be stamped out of the profile ofthe U-shaped leg of the retainer arm 14 and laterally spaced withrespect to the plane of the leg of the U-shaped retainer arm 14. Thisattached structure provides a very stabile, rigid mounting surface forthe spraying nozzle 28 which provides an attractive, compact assembly inwhich the fluid line or hose 24 can be dressed substantially entirelywithin the cavity of the U-shaped retainer arm 14 and thereby be out ofsight from the user.

With reference to prior art FIG. 2, the details of the spraying orwasher nozzle 28 are illustrated. The washer nozzle 28 includes a bodyportion and a mounting flange integrally formed therewith for mountingwasher nozzle 28 with mounting bracket 26. The fluid line 24 isconnected to an inlet nipple to provide washer fluid to an inlet port.As a result, a spray or mist is expelled from a nozzle port of theoutlet nipple.

In order to solve high cost and high weight problems, some windshieldwiper assemblies particularly teach the use of a retainer arm and wiperrod which can be made of a number of variable material layers which arefolded upon one another in various regions until the material thicknessrequired for the particular cross-section is obtained. A thin materialis bent over multiple times by approximately 180° in multiple steps inorder to brace each layer. The advantage, of course, is from arelatively thin sheet of metal, different material thickness can beobtained in different regions and this thickness can be adapted exactlyto different stresses that arise. Unfortunately, small material stresscracks, virtually invisible to the eye, can result from these multiplebending operations and as a result, such minute cracks, if they occur onthe outer surfaces, can cause excessive noise by wind passing thereoverwhen exposed to a high wind stream. Further, obviously, the multiplelayers of metal in order to accomplish the appropriate sizerequirements, may also result in higher material costs as well as higherweights due to the multiple layers which are necessary in order toprovide the appropriate structural rigidity for the torsion anddeflection forces that are known in selective areas of the windshieldwiper assembly. Generally, to enable the use of multiple layerassemblies, a thinner material is used in order to make the multiplefolds which are necessary to acquire the particular cross-section neededto resist the known deflection and torsion moments.

U.S. Pat. No. 6,505,377 B1 (Merkel et al.) discloses a wiper arm orwiper rod, element 18, for a windshield wiper assembly, the wiper rodbeing formed from multiple layers of a single thickness component sheetof metal (column 2, lines 30-39). The free or distal end of a one-piecewiper rod according to this reference is formed with four thicknesses ofmetal by a stamping operation, FIG. 8, presumably to provide the wiperrod with adequate stiffness to resist deflection or tension stressesunder aerodynamic load, to thereby maintain a wiper blade that isattached to the free end in contact with an adjacent windshield andwithout requiring an excessive wiper rod width at the outer region,which is in the field of vision of an operator of the associated motorvehicle. A known problem with the FIG. 8 configuration of the wiper armor rod of this reference is that the number of bends as a result ofstamping of the metal strip in order to achieve this configuration,requiring a 180° bend at the location of the lower detent holes(elements 56), in addition to four 90° bends to achieve suchconfiguration, can introduce cracking in outer surface layers of themetal. Such surface configuration is undesirable because it can lead toexcessive noise in the associated vehicle when the vehicle is travelingat highway speeds.

The '377 reference also discloses an alternative embodiment, theembodiment of FIG. 9-16, in which the free or distal end of the wiperrod is formed by a stamping operation in a triple thickness, as shown inFIG. 14, which also requires severe bends on each of the ends of theblank from which the rod is formed, following a 90° bend in advance ofeach 180° bend. The FIG. 14 embodiment of the invention of the '377reference, of necessity, will require a thickness sufficient toaccommodate three (3) layers of material, and it will require extrawidth of the blank from which the wiper rod is formed to provide thistriple thickness construction. The multiple layer assembly is not costeffective because of the additional processing steps to generate thevarious bends and the resultant higher weight due to the multiple layersof metal.

U.S. Pat. No. 6,732,401 B1 (Rapp), which shows an assignment to the sameassignee as the '377 patent, shows, in FIGS. 3 and 5, a wiper armassembly in which the free end has an open or box type cross-section,presumably for added rigidity in this region. The use of a box-typeconfiguration in this region adds to the required thickness of the rodor arm at a location in the field of view of the driver, which, at theleast, serves as an annoyance to the driver and is, in any case,aesthetically unattractive. Again, such configuration is not economicaland requires additional processing stops to obtain the various materialthickness configuration of the hook like end 21.

BRIEF DESCRIPTION OF THE INVENTION

The aforesaid and other problems associated with prior art wiper armconstructions are avoided by a wiper arm constructed according to thepresent invention that is fabricated from a single thickness blank of asuitable material. An inner portion of the wiper arm, which is generallyU-shaped in cross-section, is formed by a drawing operation in aprogressive die. An outer portion of the wiper arm is formed by hemminginto a double thickness, a generally C-shaped configuration with nospacing between a single thickness layer of material of the arm and anin-turned pair of material edges that extend from opposite sides of thesingle thickness layer. Such a configuration has sufficient resistanceto deflection and torsional moments under aerodynamic loads to maintaina wiper blade attached to the distal end of the wiper arm in engagementwith an adjacent windshield, it is sufficiently narrow at the distal endto avoid undue visual interference to an operator of an associatedvehicle, and it is sufficiently thin in a transverse direction to beaesthetically clean and visually undistracting. The wiper arm of thepresent invention is also lower in weight than known prior art wiper armconstructions, it is relatively inexpensive to produce due to it'ssingle piece construction, and it incorporates a more accuratelypositioned hole in a reverse turned hook end for accurate attachment ofa wiper blade to the wiper arm itself without the need of a resizingoperation to fit the hook like end between the cheeks of the supportbracket it engages. Further, the mounting bracket for attachment of thespray nozzle is formed from the extended portion of the U-shaped legs ofthe retainer arm so that no additional parts or assembly operations arerequired to attach this mounting bracket because additional material isprovided in the original blank that is carried through the progressivedie.

Accordingly, it is an object of the present invention to provide animproved, economical, light weight wiper arm for a windshield wiperassembly that is fabricated from a single thickness blank of a suitablematerial, that has a free or distal end that is narrow in the line ofsight of an operator of an associated vehicle, that is both thin in atransverse direction and is provided with sufficient resistance todeflection and torsion moments under aerodynamic load, and can be madefree of cracks and other surface irregularities that would otherwise benoisy when the associated vehicle is driven at highway speeds.

It is a further object of the present invention to fabricate an improvedwiper arm for a windshield wiper assembly that is economical tomanufacture by hemming the wiper rod portion of the retainer arm andprovide additional material in the single piece blank to enablefabrication of the mounting bracket for the attachment of the spraynozzle out of the single piece blank.

For a further understanding of the present invention and the objectsthereof, attention is directed to the drawing and the following briefdescription thereof, to the detailed description of the invention and tothe appended claims.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a plan view of a prior art construction of a windshield wiperarm assembly,

FIG. 2 is a partial view of the prior art wiper arm assembly shownwithin Circle 2 of FIG. 1;

FIG. 3 is an cross-sectional view of the prior art wiper arm along lines3-3 of FIG. 1;

FIG. 4 is a cross-sectional view of the prior art wiper arm taken alongline 4-4 of FIG. 1;

FIG. 5 is a cross-sectional view of the prior art wiper arm taken alongline 5-5 of FIG. 1;

FIG. 6 is a plan view of a blank strip for a progressive die from whichthe wiper arm according to the present invention is fabricated;

FIG. 6A is a cross-sectional view taken along line 6A-6A of FIG. 6;

FIG. 6B is a cross-sectional view taken along line 6B-6B of FIG. 6;

FIG. 6C is a cross-sectional view taken along line 6C-6C of FIG. 6;

FIG. 7 is a bottom plan view of a single piece wiper arm according tothe present invention after it has been fabricated from the blank stripof FIG. 6;

FIG. 8 is a side elevation view of the wiper arm according to thepresent invention;

FIG. 9 is a cross-sectional view rotated 90° taken along line 9-9 ofFIG. 7;

FIG. 10 is a cross-sectional view, rotated 90°, taken along line 10-10of FIG. 7;

FIG. 11 is a cross-sectional view taken along line 11-11 of FIG. 8; and

FIG. 12 is a cross-sectional view taken along line 12-12 of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

FIG. 6 is a strip layout of the stages of development of the blank forthe retainer and wiper arm as it moves through the various stationswithin the progressive die which fabricates the one-piece wiper arm. Thestrip is laid out so that two pieces are carried on either side of thecenter carrier and from the initial blanking station in the firstseveral stages of the tool the mounting bracket is partially formedupwards. Thereafter, both edge portions of the blank are formed upwardat an approximate 90° angle as shown in FIG. 7 in order to create theU-shaped form of the retainer arm. In subsequent stations, the hemmingof the arm rod portion of the retainer arm is accomplished in a twostage operation shown in FIGS. 6B and 6C wherein the first stage hemsthe edges of the blank to approximately a 45° angle which is thereafterfinished in the next station to completely hem both edges so that thehemmed edges overlie and are in direct contact with the underlyingsurface of the underlying material layer as shown in FIGS. 6C and 11.Thereafter, the mounting bracket for the attachment of the spray nozzleis cam formed to its final position shown in FIG. 12 within the two legsof the U-shaped retainer arm in two separate stations. To finalize thecompleted one piece retainer arm a slot is pierced into the rod end(FIG. 10) which is thereafter cam formed and sized into the hook likeend of the rod arm, shown in FIGS. 9 and 10, to enable the hook like endto fit between the cheeks of the support bracket of the wiper blade. Inthe final stages of the progressive die, the part is separated from thestrip so as to present the one piece wiper arm assembly incorporatingall the necessary structural elements to provide attachments for theremaining elements of a complete windshield wiper arm assembly.

The one-piece wiper arm as illustrated in FIGS. 6 through 12 accordingto the preferred embodiment of the present invention is identified byreference character 100 in bottom plan and side elevational views ofFIGS. 7 and 8 respectively. The one-piece wiper arm 100, as earlierdescribed, is formed in a single piece from a blank 100′ carried by astrip through a progressive die, with an inner end portion 100 a that isformed from the blank 100′ by progressively moving through the variousstages in the progressive die as earlier described. An outer or distalend portion 100 b is developed through the same progressive die byhemming operations as earlier described. The inner end portion 100 a ofthe one-piece wiper arm 100 generally has the configuration of adownwardly facing ∩ with a flat central or bight portion 104 that, whenmounted on the vehicle is spaced away from the windshield (not shown) ofan associated vehicle in the assembled state of the one-piece wiper arm100. The inner end portion 100 a is formed into a U-shaped configurationhaving opposed legs 106, 108 extending normally from the flat central orbight portion 104. Axially aligned openings or holes 110 are provided inthe legs 106, 108 by which the one-piece wiper arm 100 may be fastenedto a mounting head, not shown, similar to the prior art arrangement ofFIG. 1. The openings or holes 110 are stamped in the blank 100′ formedin the very beginning stations of the progressive sequence as shown inFIG. 1.

One of the legs of the U-channel section, shown in FIG. 2 as leg 106, isprovided with extended material from which the mounting bracket isfabricated to enable the attachment of the spray nozzle 28 as well asone end of the tension spring 20 as shown in prior art FIG. 1. As moreclearly shown in FIG. 12, the extended material portion or supportbracket 112, upon processing through the progressive die, is ofgenerally L-shaped configuration with a leg portion 112 a extending backtowards the central portion 104 of the U-shaped channel as well as asecond leg portion 112 b extending from an inner end of the leg portion112 a generally transverse to the leg 106 towards the leg 108 andparallel to the central bight portion 104 but spaced therefrom. Thesupport bracket 112 has an opening 114 by which an end of a coil tensionspring (not shown) may be attached to provide tension on the wiper blade(not shown) so as to bias the wiper blade against the windshield.Opposite the opening 114 is a leg extension 116 of the support bracket112 wherein is formed a detent 118 to enable mounting of the spray headand locking the spray head in place on the support bracket 112 again,similar to the illustration of the prior art in FIG. 1.

As is shown in FIG. 11, the hemmed outer end portion 100 b of theone-piece wiper arm 100 is of a double layer construction with theconfiguration of a C. This outer end portion 100 b has a centralmaterial layer portion 130 with in-turned material edge portions 132that extend parallel to the central material layer portion 130, and withno appreciable spacing between the in-turned material edge portions 132and the central material layer portion 130, the free edges of thein-turned material edge portions 132, which face the windshield of anassociated vehicle during the operation of the one-piece wiper arm 100,are touching or in very close proximity to one another. Thisconfiguration minimizes the width of the outer end portion 100 b, forminimal obstruction to the view of an operator of an associated vehicle.It is of a minimal thickness in a perpendicular direction for a clean,aesthetic appearance and optimum viewing characteristics, and impartssufficient resistance to deflection under aerodynamic load to maintainan associated wiper blade engagement with a windshield of a vehicle evenwhen the vehicle is traveling at highway speeds. Further, the FIG. 11configuration can be formed with two hemming operations in theprogressive die as shown in FIGS. 6B and 6C. The first operation hemsthe material at approximately a 45° angle as shown in FIG. 6B. Thesecond stage of hemming completely hems both ends so that the hemmedends come into complete contact with the central material layer portion130 and with each other. The hemming operations do not result in anysurface irregularities in that portion of the blank 100′ and theobjectionable noise is not experienced that can result in a wiper armhaving external surface cracks when the associated vehicle is travelingat highway speeds.

An outermost end portion 100 c of the outer end portion 100 b of theone-piece wiper arm 100 is reversely folded by a cam form operation toform the hook end 120 which is spaced from and extends parallel to aportion of the outer end portion 100 b that is thereabove. Thisoutermost end portion 100 c of the outer end portion 100 b is theportion of the one-piece wiper arm 100 that is provided with the opening126, and the spacing between the outermost end portion 100 c and theportion of the outer end portion 100 b thereabove provides a clearancefor the proper attachment of a wiper blade to the one-piece wiper arm100 and for the easy removal of the wiper blade when it is required toreplace the wiper blade. The progressive die operation final sizes thewidth of the hook end 120 in order to fit the hook end 120 between thecheeks of the support bracket of the wiper blade.

Although the best mode contemplated by the inventor for carrying out thepresent invention as of the filing date hereof has been shown anddescribed herein, it will be appreciated by those skilled in the artthat suitable modifications, variations, and equivalents be made withoutdeparting from the scope of the invention, such scope being limitedsolely by the terms of the following claims and the legal equivalentsthereof.

1-4. (canceled)
 5. A method of making a unitary wiper arm, said methodcomprising the steps of: providing a single thickness blank adapted tobe carried through a progressive die; forming an inner portion of saidunitary wiper arm in the form of a generally upward formed cross-sectionby a drawing operation in said progressive die, said upward formedcross-section having a bight portion with extending opposed legs;forming an outer portion of said unitary wiper arm into a generallydouble thickness configuration by in-turning said material edges thatextend from opposing sides of said single thickness layer of material bya hemming operation in said progressive die; removing said formed wiperarm from said single thickness blank carried through said progressivedie.
 6. The method as claimed in claim 5 further comprising the step of:forming axially aligned openings in said extending opposed legs topermit mounting of said unitary wiper arm to a mounting head.
 7. Themethod as claimed in claim 5 further comprising the step of: providingone of said extending opposed legs with a material extension; and camforming said material extension from said one of said opposed legs intoa support bracket located between said extending opposed legs.
 8. Themethod as claimed in claim 7 further comprising the step of: attaching aspray nozzle to said support bracket located between said extendingopposed legs.
 9. The method as claimed in claim 5 wherein said formingan outer portion of said unitary wiper arm further comprises the stepof: forming said in-turned material edge portions over a centralmaterial layer with no appreciable spacing between said in-turnedmaterial edge portions and said central material later portion to formsaid double thickness configuration, said free edges of said in-turnedmaterial edge portions touching or in very close proximity with oneanother.
 10. The method as claimed in claim 5 further comprising thestep of: cam forming the outermost end portion of the unitary wiper arminto a reversely folded hook portion which is spaced from and extendsparallel to a portion of the hemmed outer portion of said unitary wiperarm, to provide a spacing for the proper attachment of a wiper blade tothe unitary wiper arm when it is required to remove said wiper blade.11. The method as claimed in claim 6 further comprising the step of:final forming the width of said reversely folded hook portion so as toenable easy fitting of said hook portion between the cheeks of thesupport bracket attached to said wiper blade.